ganfra
1 year ago
2 changed files with 4 additions and 206 deletions
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@@ -1,204 +0,0 @@
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/* |
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* Copyright (c) 2023 New Vector Ltd |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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package io.element.android.libraries.designsystem.components.blurhash |
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import android.graphics.Bitmap |
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import android.graphics.Color |
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import kotlin.math.cos |
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import kotlin.math.pow |
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import kotlin.math.withSign |
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/** |
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* Extracted from https://github.com/woltapp/blurhash/blob/master/Kotlin/lib/src/main/java/com/wolt/blurhashkt/BlurHashDecoder.kt |
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*/ |
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object BlurHashDecoder { |
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// cache Math.cos() calculations to improve performance. |
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// The number of calculations can be huge for many bitmaps: width * height * numCompX * numCompY * 2 * nBitmaps |
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// the cache is enabled by default, it is recommended to disable it only when just a few images are displayed |
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private val cacheCosinesX = HashMap<Int, DoubleArray>() |
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private val cacheCosinesY = HashMap<Int, DoubleArray>() |
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/** |
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* Clear calculations stored in memory cache. |
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* The cache is not big, but will increase when many image sizes are used, |
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* if the app needs memory it is recommended to clear it. |
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*/ |
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fun clearCache() { |
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cacheCosinesX.clear() |
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cacheCosinesY.clear() |
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} |
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/** |
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* Decode a blur hash into a new bitmap. |
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* |
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* @param useCache use in memory cache for the calculated math, reused by images with same size. |
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* if the cache does not exist yet it will be created and populated with new calculations. |
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* By default it is true. |
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*/ |
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fun decode(blurHash: String?, width: Int, height: Int, punch: Float = 1f, useCache: Boolean = true): Bitmap? { |
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if (blurHash == null || blurHash.length < 6) { |
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return null |
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} |
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val numCompEnc = decode83(blurHash, 0, 1) |
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val numCompX = (numCompEnc % 9) + 1 |
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val numCompY = (numCompEnc / 9) + 1 |
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if (blurHash.length != 4 + 2 * numCompX * numCompY) { |
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return null |
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} |
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val maxAcEnc = decode83(blurHash, 1, 2) |
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val maxAc = (maxAcEnc + 1) / 166f |
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val colors = Array(numCompX * numCompY) { i -> |
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if (i == 0) { |
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val colorEnc = decode83(blurHash, 2, 6) |
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decodeDc(colorEnc) |
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} else { |
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val from = 4 + i * 2 |
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val colorEnc = decode83(blurHash, from, from + 2) |
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decodeAc(colorEnc, maxAc * punch) |
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} |
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} |
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return composeBitmap(width, height, numCompX, numCompY, colors, useCache) |
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} |
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private fun decode83(str: String, from: Int = 0, to: Int = str.length): Int { |
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var result = 0 |
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for (i in from until to) { |
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val index = charMap[str[i]] ?: -1 |
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if (index != -1) { |
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result = result * 83 + index |
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} |
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} |
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return result |
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} |
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private fun decodeDc(colorEnc: Int): FloatArray { |
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val r = colorEnc shr 16 |
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val g = (colorEnc shr 8) and 255 |
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val b = colorEnc and 255 |
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return floatArrayOf(srgbToLinear(r), srgbToLinear(g), srgbToLinear(b)) |
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} |
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private fun srgbToLinear(colorEnc: Int): Float { |
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val v = colorEnc / 255f |
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return if (v <= 0.04045f) { |
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(v / 12.92f) |
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} else { |
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((v + 0.055f) / 1.055f).pow(2.4f) |
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} |
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} |
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private fun decodeAc(value: Int, maxAc: Float): FloatArray { |
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val r = value / (19 * 19) |
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val g = (value / 19) % 19 |
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val b = value % 19 |
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return floatArrayOf( |
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signedPow2((r - 9) / 9.0f) * maxAc, |
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signedPow2((g - 9) / 9.0f) * maxAc, |
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signedPow2((b - 9) / 9.0f) * maxAc |
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) |
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} |
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private fun signedPow2(value: Float) = value.pow(2f).withSign(value) |
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private fun composeBitmap( |
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width: Int, height: Int, |
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numCompX: Int, numCompY: Int, |
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colors: Array<FloatArray>, |
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useCache: Boolean |
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): Bitmap { |
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// use an array for better performance when writing pixel colors |
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val imageArray = IntArray(width * height) |
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val calculateCosX = !useCache || !cacheCosinesX.containsKey(width * numCompX) |
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val cosinesX = getArrayForCosinesX(calculateCosX, width, numCompX) |
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val calculateCosY = !useCache || !cacheCosinesY.containsKey(height * numCompY) |
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val cosinesY = getArrayForCosinesY(calculateCosY, height, numCompY) |
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for (y in 0 until height) { |
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for (x in 0 until width) { |
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var r = 0f |
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var g = 0f |
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var b = 0f |
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for (j in 0 until numCompY) { |
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for (i in 0 until numCompX) { |
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val cosX = cosinesX.getCos(calculateCosX, i, numCompX, x, width) |
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val cosY = cosinesY.getCos(calculateCosY, j, numCompY, y, height) |
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val basis = (cosX * cosY).toFloat() |
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val color = colors[j * numCompX + i] |
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r += color[0] * basis |
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g += color[1] * basis |
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b += color[2] * basis |
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} |
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} |
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imageArray[x + width * y] = Color.rgb(linearToSrgb(r), linearToSrgb(g), linearToSrgb(b)) |
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} |
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} |
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return Bitmap.createBitmap(imageArray, width, height, Bitmap.Config.ARGB_8888) |
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} |
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private fun getArrayForCosinesY(calculate: Boolean, height: Int, numCompY: Int) = when { |
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calculate -> { |
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DoubleArray(height * numCompY).also { |
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cacheCosinesY[height * numCompY] = it |
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} |
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} |
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else -> { |
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cacheCosinesY[height * numCompY]!! |
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} |
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} |
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private fun getArrayForCosinesX(calculate: Boolean, width: Int, numCompX: Int) = when { |
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calculate -> { |
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DoubleArray(width * numCompX).also { |
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cacheCosinesX[width * numCompX] = it |
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} |
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} |
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else -> cacheCosinesX[width * numCompX]!! |
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} |
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private fun DoubleArray.getCos( |
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calculate: Boolean, |
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x: Int, |
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numComp: Int, |
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y: Int, |
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size: Int |
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): Double { |
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if (calculate) { |
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this[x + numComp * y] = cos(Math.PI * y * x / size) |
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} |
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return this[x + numComp * y] |
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} |
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private fun linearToSrgb(value: Float): Int { |
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val v = value.coerceIn(0f, 1f) |
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return if (v <= 0.0031308f) { |
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(v * 12.92f * 255f + 0.5f).toInt() |
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} else { |
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((1.055f * v.pow(1 / 2.4f) - 0.055f) * 255 + 0.5f).toInt() |
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} |
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} |
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private val charMap = listOf( |
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'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', |
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'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', |
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'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', |
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'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '#', '$', '%', '*', '+', ',', |
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'-', '.', ':', ';', '=', '?', '@', '[', ']', '^', '_', '{', '|', '}', '~' |
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) |
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.mapIndexed { i, c -> c to i } |
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.toMap() |
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} |
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